Portable, rechargeable battery pack



FIG. 1 is a perspective view of a portable rechargeable battery pack showing my new design;

FIG. 2 is a front elevation view thereof;

FIG. 3 is a right side view thereof;

FIG. 4 is a left side view thereof; and,

FIG. 5 is a rear elevation view thereof. 

The ornamental design for a portable rechargeable battery pack, as shown. 